1. Field of the Invention
The invention relates generally to measurement, communication, and performance monitoring apparatus used in the installation and operation of geothermal well power systems of the kind providing for the generation of electrical or other power by utilizing energy from subterranean geothermal sources and, more particularly relates to electromagnetic transmission lines for transmitting operating data of such geothermal power systems to the earth's surface.
2. Description of the Prior Art
The present invention is designed for use in operating geothermal well power generation systems of the general kind disclosed in U.S. Pat. No. 3,824,793 entitled "Geothermal Energy System and Method" issued July 23, 1974 and U.S. Pat. No. 3,938,334 issued Feb. 17, 1976 entitled "Improved Geothermal Energy Control System and Method" and U.S. Pat. No. 3,910,050 issued Oct. 7, 1975 entitled "Geothermal Energy System and Control Apparatus", all of which are assigned to the Sperry Rand Corporation. The foregoing illustrate features of a geothermal energy transfer and utilization system that extracts thermal energy stored in hot solute-bearing well water to generate super-heated steam from an injected flow of clean water; the super-heated steam is then used in operating a turbine-driven pump at the well bottom, pumping the hot solute-bearing water at high pressure and in liquid state to the earth's surface, where transfer of its heat content to a closed-loop boiler-turbine-alternator combination is effected for the generation of electrical or other power. Cooled, clean water is regenerated by the surface-located system for re-injection into the deep well and the residual, concentrated solute-bearing water is pumped back into the earth.
Geothermal wells of this and other types may be logged to a useful extent by methods applied previously in the oil well industry. In such tests, a canister which may contain sensors, a battery, and a recorder is lowered into the well and is then brought back to the earth's surface where the recorded data is retrieved. This time-consuming method is undesirable even in the oil well application, as it is not a real-time method and requires removal of equipment from the well. Where an operating system such as a geothermal well pump is present, removal of the pump system is not economical and only secondary means of obtaining data from the deep well pump site are available.
For example, in the aforementioned application U.S. Pat. No. 3,910,050 reliable operation of the system is assured by a control arrangement in which the pressure of clean water entering the subterranean steam generator determines the rate of mass flow through the pump-driving steam turbine and consequently determines the proper pressure of the hot pumped well water. By control of the output pressure of the clean water pump at the earth's surface, the pumped hot well water pressure is determined. The novel arrangement also permits controlled starting and stopping of the deep well pumping apparatus, permitting the bearings thereof to be adequately lubricated at all times. While the arrangement of application Ser. No. 487,429 is advantageous in an established geothermal power system, direct measurements of primary parameters that instantaneously reflect the efficiency of operation of the deep well geothermal pump system, parameters whose values are particularly of interest during installation and initial operation of the system and even during its continued operation, are not conveniently provided by it. When a change in the output characteristics of a pumped well is observed only at the well head, it is difficult or impossible to assign the cause of the change to a particular problem at the deep well pump location. Thus, more direct evidence is needed in addition to control signals of the general type previously available.